Possible bug with unknown args to function?

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•

jrh

I was testing espruino on the Linux command line (while waiting for my boards to be shipped) and ran across this error. Is this a bug, or a feature?

$ espruino
Interactive mode.
Size of JsVar is now 32 bytes
Size of JsVarRef is now 4 bytes
Added SIGINT hook
Added SIGHUP hook
Added SIGTERM hook

 ____                 _ 
|  __|___ ___ ___ _ _|_|___ ___ 
|  __|_ -| . |  _| | | |   | . |
|____|___|  _|_| |___|_|_|_|___|
         |_| espruino.com
 2v04.8 (c) 2019 G.Williams

Espruino is Open Source. Our work is supported
only by sales of official boards and donations:
http://espruino.com/Donate

>function foo(x,y) {
:for (var i = 0; i < arguments.length; i++) {
:console.log(arguments[i]);
:}
:}
=function (x,y) { ... }
>foo(1,2)
1
2
=undefined
>foo(100)
100
Uncaught ReferenceError: "1" is not defined
 at line 2 col 24
console.log(arguments[i]);
                       ^
in function "foo" called from line 1 col 8
foo(100)
       ^
>quit()
=undefined
>

The source was cloned from github and compiled on Ubuntu 16.04.6 LTS. I got the same error on an OS X build as well. It was built with the following commands:

export BOARD=LINUX
source ./scripts/provision.sh $BOARD
 make clean && RELEASE=1 BOARD=$BOARD make

I saw this post Functions with unknown amount of args. but I didn't get the same results.

•

maze1980 in reply to @jrh

Yes it's a bug. arguments.length is set to the number of arguments if the number of provided arguments is higher (and/or equal) to the number specified arguments in the function definition. But it is not set to the number of arguments if the number of provided arguments is smaller.

As workaround define the function without arguments, arguments.lengthwill be always correct.

function foo(x,y) {
  console.log("arguments.length=" + arguments.length);
  //console.log("x=" + x);
  //console.log("y=" + y);
  //for ( var i=0; i < arguments.length; i++ ) {
  //  console.log("typeof(arguments["+ i + "])=" + typeof(arguments[i]));
  //  console.log("arguments["+ i + "]=" + arguments[i]);
  //}
}
function bar() {
    console.log("arguments.length=" + arguments.length);
}
foo();
foo(1);
foo(1,2);
foo(1,2,3);
bar();
bar(1);
bar(1,2);
bar(1,2,3);

Possible bug with unknown args to function?

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